Accumulation of marine litter is a worldwide growing problem of pollution in seas. Although it is recognized as one of the major pollution types for the Black Sea, very few studies can provide quantitative data and there are no data at all on solid wastes of the Black Sea seabed. This study was therefore aimed at investigating the abundance and composition of solid wastes in the southwestern Black Sea. Litter items were collected by trawling in October 2007, and in February and April 2008, at depths ranging from 25 m to 100 m. The solid waste concentration on the seabed showed a large variability (with zones ranging from 128–1320 items km– 2 and 8–217 kg km-2). Marine litter concentrations were higher than in the Mediterranean Sea, consisting mainly of plastic materials. Most items were fragmented, which indicated that they had spent a long time at sea, and this made their identification difficult. Only 8 items had legible labels, 2 of them being Turkish and 6 foreign. This suggested that marine litter is a trans-boundary problem, not only in the oceans, but also for enclosed seas like the Black Sea. The situation needs to be monitored all over the basin using standardised methods in order to develop regionally valid and effective solutions.
Marine litter is a growing problem worldwide. Even though this fact has been recognized for nearly 30 years, the pollution of marine environments by solid waste could not be averted and marine debris on seabeds reached quantities as high as 101 000 items km−2 (Galgani et al., 2000). Marine debris was defined as “any persistent, manufactured or processed solid material discarded, disposed of, or abandoned in the marine and coastal environment” (United Nations Environment Programme (UNEP), 2005). The sources of marine debris can be continental, marine or both (mixed origin) and depend on the characteristics (distance to shore, presence of shipping lines or touristic activity, enclosed environment) of the studied area. There has been an increase in the quantity of the marine waste since the invention and fast development of plastic materials. The solidity and durability of plastic materials make them useful, but also very persistent in the environment once thrown away. The resistance of plastic to degradation, combined with its continuous discard into the sea, make it the largest contaminant found in the marine environment (Derraik, 2002). Besides plastic, a large variety of other persistent materials sink to the seabed after floating on the surface for a while. Contingent on their sources and driving forces, waste materials may be distributed in large distances and depths at sea (Schrey and Vauk, 1987). Litter in the sea affects marine fauna through entanglement, or ingestion of such materials by animals (Tonay et al., 2007). It also has negative economic impacts through damages to navigation, (such as tangling up propellers, blocking cooling water intakes of engines) to fishery activities, and is an esthetic concern for tourism.
There have been many studies on marine debris collected from Mediterranean seabeds (Bingel et al., 1987; Galgani et al., 1995; Galil et al., 1995; Galgani et al., 1996; Stefatos et al., 1999; Galgani et al., 2000; Yilmaz et al., 2002; Katsanevakis and Katsarou, 2004; Koutsodendris et al., 2008); whereas there is almost no data on the Black Sea (Clunie and Hendricks, 1995; BSC, 2007). The Black Sea is subject to a number of international, regional and national legal instruments which, to some extent, are predestined to regulate marine litter pollution. Among them, the Bucharest Convention is the most effective on land-based marine litter; whereas the International Convention for the Prevention of Pollution from Ships (MARPOL 73/78) is the basic regulation for shipping-based litter. The Black Sea is defined as a “Special Area” under Regulation 5 of Annex V (MARPOL), according to which any discharges of garbage into the sea are prohibited. However, MARPOL requires riparian states to have adequate port facilities to deal with marine litter, and in 2010 this was not yet implemented. Consequently, the Black Sea is not yet treated as a Special Area.
The Black Sea is an almost totally enclosed sea, whose unique connection with the Mediterranean Sea is the narrow passage of the Turkish Straits System (TSS). Many rivers, including the second, third and fourth major rivers in Europe discharge into the Black Sea. It is an important shipping route and is subject to intense fishing activities. As a result, it is very vulnerable to any kind of additional pollution, including solid wastes. Data regarding marine litter quantities is still very scarce in this area, however. Although the importance of the problem is recognized (Commission on the Protection of the Black Sea against Pollution (BSC), 2007), very few studies have provided quantitative data and there is no data at all on solid wastes from the Black Sea seabed. Litter pollution in the Black Sea has been estimated to be as heavy as the rest of the world seas according to a model based on the Mediterranean and Black Sea's maritime traffic (Clunie and Hendricks, 1995).
The aim of this study was to investigate the abundance and composition of solid wastes on the western coast of the Turkish Black Sea seabed and to establish baseline data in order to develop regionally valid and effective solutions for managing marine litter pollution.
The study area was located in the western part of the Turkish Black Sea coast (Figure 1) and was considered in three parts in order to be spatially analysed. At the western part of the study area, samples were taken between 49 and 77 m depth on the continental shelf. In the central part, close to the Istanbul Strait northern exit, samples were taken very close to shore, between 21 and 25 m depth, except the Oct 2 station which was 58 m deep. On the eastern part of the study area, samples were collected close to the beginning of the continental slope, between 76 and 103 m depth. Small streams discharge in the area, where human population is restricted to a few small villages. The only big city close to the area is Istanbul, where an integrated solid waste management system has been implemented (Berkun et al., 2005). Floating solid wastes originating from the city are not expected to come to the Black Sea, since the circulation system transports surface water from the Black Sea to the Marmara Sea. Only sunken solid wastes can be transported from the Istanbul Strait to the Black Sea via the lower current with heavier Mediterranean water. There is intensive fishing activity in the area except during the prohibited period between May 1st-September 1st. Approximately 200 fishing boats are registered to the village Rumeli Feneri (Anonymous, 2004). This area is also on an important shipping lane with big tanker and cargo ship passage. Station Feb 1 is within the anchorage area where ships wait for their passage through the Istanbul Strait.
Litter items were collected by trawling in the Turkish part of the western Black Sea with a 32 m-long research vessel R/V Yunus-S, in October 2007 (4 hauls: Oct 1–Oct 4); February 2008 (4 hauls: Feb 1-Feb 4); and April 2008 (6 hauls: Apr 1–Apr 6).The net opening was 21.6 m with a mesh size of 22 mm which was small enough to allow selection of various types of litter. Trawls were conducted with a speed kept at 2.5–2.7 knots, lasting 30 or 45 minutes. Litter items caught in nets were collected, dried and sorted according to types of materials and use. Twelve types of materials were identified: hard plastic, nylon (as soft plastics), cloth, paper, metal, wood, vinyl, glass, rubber, fibres, composite and cellulose acetate. They were also grouped into following 14 categories according to original use: general packaging, beverage packaging, food packaging, cloth, wooden plank, net/fishline, rope/hawser, cleaning supplies, shoes, mechanical instruments, cigarette butts, artificial leather, pieces of nylon and unidentified. Pieces of nylon were intentionally not put in the general packaging category in order to underline the high number. It was not possible to recognize the original shape and use of those pieces of nylon. Marine debris items were then counted and weighed. The swept area method (Gunderson, 1993) was applied for the calculation of the amount of litter on the seabed, as number of items per unit area (km2) and as total weight of items per unit area.
Marine debris was present in all stations. A total of 244 solid waste materials were collected and the total weight was 10.62 kg. The concentration of marine litter ranged from 128 items km−2 to 1320 items km−2, whereas the density in weight ranged between 0.30–218 kg km−2. The average concentration of debris for the total sampled area was 541 items km−2. Large variations of number and weight of items within stations were recorded. The high variability of litter abundances within one season did not allow relating the variability to seasonal effect. No relationships between depth and distance to shore were found. However, there seemed to be a decreasing tendency of number of items in the direction west-east (R2= 0.5) (Figure 2). Considering the three areas, mean concentrations were 936 items km−2 (±383) in the western area, 402 items km−2 (±225) in the central area and 228 items km−2 (±80) in the eastern area.
Soft plastic (nylon) materials dominated the composition of waste materials (79.6%) followed by hard plastic (10.3%). All other materials had contributions less than 4% (Figure 3). Most of the nylon materials were composed of small pieces and a few of them were entire nylon bags or secondary packagings. Among usage categories, nylon pieces were the most frequent (73.6%) followed by general packaging (10.6%) and beverage packaging (4.7%) (Figure 4).
Only 8 pieces of debris had legible writing, with 3 of them being in Turkish (2 of them being nylon bags) and 5 being in foreign languages (food packaging 1-Russian [EAN country code], food packaging 2-Bulgarian, detergent packaging in Italian, a nylon bag in good condition-Russian, and 1 label).
Considering the results of the putative three areas, marine debris concentration was very high on the western part, compared to others from the Mediterranean seabed (Galgani et al., 1996; Stefatos et al., 1999; Koutsodendris et al., 2008), except the accumulation zones (Galgani et al., 2000) and some densely populated and industrialized area in gulfs (Katsenavakis and Katsarou, 2004). Litter concentration in the central area was also significant, compared to the Adriatic Sea (Galgani et al., 2000) (380 items km−2), the Patras Gulf (240 items km−2) (Stefatos et al., 1999), (500 items km−2) (Koutsodendris et al., 2008) and the Gulf of Lion (Galgani et al., 1996) although the depths and localities of the study areas are different. Litter concentration in the eastern area was moderate, in comparison to studies cited above. This decreasing tendency may be explained by the circulation pattern in the western Black Sea, where there is a cyclonic gyre taking water masses from north to south, intersected with a small scale gyre in the southwestern area (Korotaev et al., 2003). Stations of the western area may be in part of an accumulation zone. Station Apr 2 which had less debris concentration than others, was the closest to shore. These stations are also on the major shipping lane from Istanbul strait to Bourgas and Constanta. However, the concentrations at the stations in the eastern area were less important, although these stations were located on the shipping lane to Russia, Ukraine and Georgia. Among the stations of the central area, the concentration of Feb 1 was very high probably due to its location within the anchorage area.
Weights of items were dependent on material type and could result in misleading evaluations. For example, stations Oct 1, Apr 2 and Apr 5 had concentrations around 300 items km−2, but weights were very different because of the presence of a large wooden material in Oct 1 station (217 kg km−2), light nylon and paper materials in Apr 5 (0.30 kg km−2) and another piece of wood in Apr 2 (80 kg km−2). These concentration values were comparable to those found in the studies of Mediterranean seabed marine litter.
Plastic as a whole is the most frequent litter material in accordance with most other studies (Derraik, 2002). In this study, there was a dominance of soft plastic materials which were mostly frayed and fragmented. The condition of these materials was probably due to their long time exposure to the sea.
It is not generally easy to identify the source of litter items with complete certainty. Fishing gears are generally the most attributable debris source of seabed pollution. Sixteen fishing gears were found among 244 total solid waste materials, which clearly showed that fisheries activities could be the main source of litter on the southwestern Black Sea seabed. It is possible to suggest that most of the marine litter originated from land, because of the high number of nylon materials. Nevertheless, in spite of the nearest land being the Turkish coast, very few had Turkish markings (3 of a total of 244 solid wastes). Also, the major circulation pattern is in the opposite direction, bringing water masses from north to south. In fact, most debris was frayed and markings erased, which indicated they had spent a long time at sea.
Detergent packaging found was probably dumped from a vessel, but is a good example of material being misidentified. It was marked in Italian which is considered an indicator of vessel based litter but normally detergent packaging is considered of land origin and so was placed in this category (Koutsodendris et al., 2008). All other wastes were from countries bordering the Northern coasts of the Black Sea and were probably dumped from vessels. As the litter distribution on the sea bottom is probably affected by hydrodynamic circulation (Galgani et al., 2000), it is also possible that wastes dumped from the Northern coasts were transported by currents. This situation clearly shows that it is not enough for a country bordering an enclosed sea to implement all measures to prevent marine litter pollution, all riparian countries must fulfil their obligations to properly manage solid wastes, both terrestrial and that dumped from vessels.
This is the first study to quantify marine debris present on the Black Sea seabed. Marine litter concentrations were higher than that in the Mediterranean Sea. Plastic materials make up the dominant solid waste. The Black Sea, an enclosed sea surrounded by many countries, with a highly dynamic circulation system and a large drainage basin, an important shipping route, with many fisheries and tourism areas, receives solid wastes from various sources. Although some legal instruments destined to control marine litter exist for the Black Sea, “A Special Area” under MARPOL 73/78, they are not yet correctly applied. Marine litter issues of the entire basin need to be monitored using standardized methods in order to properly quantify these problems, find out their sources, and develop appropriate measures to mitigate such pollution.
The authors would like to thank Istanbul University Fisheries Faculty Research Vessel R/V YUNUS-S crew for their efforts, Turkish Marine Research Foundation (TUDAV) for the support to this study and Dr. Ayaka Amaha Öztürk for kindly reading an early version of the manuscript.